The EU-funded three-year NELLHI project has concluded after successfully developing a new stack design of solid oxide fuel cells, from an all-European supply chain. NELLHI combined European know-how in single cells, coatings, sealing, and stack design to produce a novel high-performance 1 kW SOFC stack along with with the proof of concept of a 10 kWe SOFC stack.
Solid oxide fuel cells (SOFC) produce the highest efficiencies of any electrical generation, above combustion engines, gas turbines or other fuel cells. Key potential applications for SOFC systems include residential combined heat and power systems (CHP), automotive vehicles, and electrolysis. In an SOFC electrolysis system, fuel cells convert excess power from renewable generation to turn water into hydrogen, addressing intermittency and storage issues for wind and solar.
Key challenges such as high costs, production at scale and capital investment have hampered widespread deployment of SOFCs.
Participants of the NELLHI project report that their results address two of these concerns, in achieving the project’s main objectives, which were:
Developing high-performance SOFC stacks at low cost: Results showed more than 70% stack gross efficiency and excellent resilience towards load cycles. The project found its stacks were “ready for integration in any clean power-generating system and implementation in the energy market.” Stacks were designed and assembled with optimized interconnections and seals.
Optimizing high-performance cells with low temperatures: Stack performance depends on the electrochemical properties of its cells. European fuel cell manufacturer Elcogen developed an optimal microstructure using particular materials to decrease operational temperatures to 650 ˚C—compared to conventional temps of 750-800°C. Cell dimensions were also increased and Elcogen developed a highly reproducible route to increase mass production rates.
Newly patented seals: The NELLHI project developed and tested a new material formula for cell fuel cell seals. These gaskets are resistant to high temperatures and extreme atmospheres. The design was patented during the project and is now commercially available from UK company Flexitallic.
Companies and research organisations from Estonia, Finland, Italy, Sweden, Belgium, Germany and the UK were involved.
NELLHI received €1.6 million (US$1.9 million) in funding from Europe’s Fuel Cells and Hydrogen Joint Undertaking (FCH JU) in support of the expected costs amounting to just under €3 million (US$3.6 million).
Participants in the NELLHI project included Estonian fuel cell manufacturer Elcogen; Italian new technologies and energy agency ENEA; Finnish technical research center VTT; UK engineered seal company Flexitallic; Belgian fuel cell component company Borit; Swedish engineering company Sandvik; and German institute for environmental technology CUTEC.
The FCU has awarded grants for three follow up studies following NELLHI project:
The first is looking into the adoption of NELLHI stack development for integration in a 50 kWe combined heat and power generation system, under the InnoSOFC name.
The second project, qSOFC, is automating NELLHI stack mass-manufacture to reduce costs down to 1000 €/kW at 10 MW/year production volumes.
The third, DEMOSOFC, is studying the implementation of a 50 kWe SOFC system with NELLHI-based stacks fed with biogas from a municipal waste water-treatment plant.
SOFCs. In a solid oxide fuel cell, the fuel is fed to the anode side, where the high temperature allows it to be separated into its essential constituents. With hydrocarbon fuels, these are hydrogen (H2) and carbon monoxide (CO).
H2 reacts electrochemically to generate two electrons per molecule of hydrogen. This current is made to flow across the electrical load that needs to be powered, and reacts at the cathode side with the air that is fed there. Every two electrons generate an oxygen ion, wich migrates across the gas-tight electrolyte to the anode, where it reacts with the hydrogen to release again the two electrons that generated the oxygen ion, effectively closing the circuit. In the process, the only by-product formed is water.
In the case of CO, the process by-product is CO2. The outlet of the SOFC therefore produces a clean and relatively pure mixture of water and carbon dioxide. Thus, if necessary, the carbon dioxide can be separated and sequestered much more easily than is the case with the by-product flows from combustion, where large quantities of nitrogen, contained in the air used for combustion, dilute the CO2 content and make it energy and cost-intensive to separate.
To turn the stack of cell to a fully functional power generating systems several auxiliary components (the so-called balance-of-plant, BOP) have to be integrated, taking care of fuel pre-treatment, power management and heat exchange.
In order to preserve the high efficiency of electrochemical conversion in the SOFC, the BOP often needs to be designed and produced specifically to optimize the integration and minimize parasitic losses.